Thermoanalytical and other physical methods will be used in an integrated approach to related problems involving the physical behavior of lipids and lipoprotein systems. Special emphasis will be placed upon scanning calorimetry, together with dilatometry, monolayer studies, electrochemical methods, and other more conventional approaches. The mechanism for control of fatty acid composition of membranes, especially with respect to its response to temperature, will be studied. A new principle of control based upon the thermodynamic state of the membrane bilayer itself, will be elucidated. A physical rationale for the lipid class composition of membranes will be developed, with initial emphasis upon gram-positive bacteria. A search will be made for the existence of glass transitions in lipids and membranes will be made, in order to use such transitions to better understand membrane structure and function. The role of protein in the function of lung surfactant will be clarified, and the properties of lung surfactant under physiologically realistic conditions will be determined. The interaction of cholesterol with lecithin bilayers will be examined, with the major emphasis upon dilatometric methods. An automated scanning dilatometer has been constructed for this purpose.